Method and apparatus for ultrasonic sterilization



INVENTOR.

Dec. 2, 1969 s. s. FISI-MAN METHOD AND APPARATUS FOR ULTRASONIC STERILIZATION Filed March 8, 1965 -Il lll 'Il lul. Il

United States Patent Oi 3,481,687 METHOD AND APPARATUS FOR ULTRASONIC STERILIZATION Sherman S. Fishman, P.O. Box 321, San Francisco, Calif. 94101 Filed Mar. 8, 1965, Ser. No. 437,921 Int. Cl. A611 .7/ U.S. Cl. 21-54 11 Claims ABSTRACT OF THE DISCLOSURE An ultrasonic scrubbing device into which an arm and hand is immersed for cleaning and bactericidal activity by the combination of ultrasonic scrubbing with soaps and germicidal chemicals in the solution in the tank.

This invention relates to sterilizers as used to sterilize medical and surgical instruments; medical appliances; dental tools and fixtures; syringes, needles and other small devices. Additionally, the method may be applied to the surgical hand scrub. The surgical hand scrub is traditionally performed today much the same as it has been for the past 100 years. It was Lord Lister, an English surgeon, who first used sterile instruments during operations (1867). Lister used a device to produce an aerosol of carbolic acid which produced a sterile field. The procedure today requires strict adherence to a schedule of hand scrubbing with a stiff bristle brush for at least four minutes on each hand and following a specified pattern of coverage. The time requirements are reduced for surgical scrubs following the initial one. Specified soaps and antiseptics or a combination are used. The problems associated with this method include unsupervised performance of the scrub procedure which permits laxity to go uncorrected, non-uniform execution of the scrub pattern which permits varying degrees of effectiveness of the method from individual to individual, physical abuse of the epidermis by the abrasiveness of the scrubbing brush and depletion of natural oils normally present in the skin due to the prolonged exposure to emulsifying soaps.

The problem of effective sterilization of medical and dental instruments remains today the subject of many methods and materials. Most common is a hot, wet sterilization by means of a steam autoclave. Some medical devices cannot be heated yet they require sterilization. To do this, chemical sterilants in liquid and gasl form are available which will sterilize at room temperature with exposures of suitable duration. The time required may be quite extensive as in Ithe case of ethylene oxide gas which requires at least 16 hours; or 70% ethyl alcohol which requires 45 minutes. The recent development of the ultrasonic technique of removing surface contamination opens an opportunity for the application of this new device to cleaning and sterilization problems in the hospital.

Cavitation is a potent erosive force produced in liquids exposed to periodic oscillatory forces. Cavitation produced by an ultrasonic cleaning machine has been shown to be a rapid and effective mechanical scrubber which frees a surface of adherent foreign matter. In 1959 Levin published on chemical sterilization of dental hypodermic syringes and needles (Dept. of Defense Medical Technicians Bulletin, :(1), 29,1959) and in a private communica-tion of Apr. 19, 1961 expressed optimism about the possible uses of ultrasonic sterilization in dentistry. The use of ultrasonics began to appear in publications and Shaner (Shaner, E. O., The Bactericidal Effects of Cavitation During the Ultrasonic Cleaning of Dental Instruments With Benzalkonium Chloride, Jrnl. of Dist. of Col. Dental Soc., October 1962) reports effective steriliza- 3,481,687- Patented Dec. 2, 1969 ice tion of dental burrs after ultrasonic treatment of the burrs for two minutes in benzaldonium chloride. Black (Black, E. R., A Study of the Effect of Ultrasonic Energy on the Activity of a surface Active Quaternary Ammonium Germicide, thesis, Graduate School of Indiana University School of Dentistry, 1964) has found that there is a difference in the effectiveness of ultrasonics depending on the frequency. He showed that kc. was more effective on S. aureus and 20 kc. was more effective on E. col in producing negative turbidity readings in broth cultures having a quantity of Zephiran in it. However, prolonged irradiation produced equally lethal effects.

In considering the use of ultrasonic potentiated bactericidal agents in an automated surgical hand scrub it becomes apparent that more than equipment considerations are involved. Any method which applies a physical and chemical force to the human organism must not have harmful biological side effects. Ultrasonic energy is known to have a powerful degassing effect. Gases in solution are rapidly driven out of solution. This same circumstance would apply to biological fluids such as blood. To counteract the biological effects of ultrasound the equipment employed must operate at an energy level below the threshold of biological response. A common known means of reducing the output power of an ultrasonic cleaning machine is to lower the voltage to the generator by means of an auto-transformer. By this technique operating power levels can be reduced to the minimum required for cavitation. To further reduce the radiation dose the source of radiation is changed in relative position.

This invention relates to the method and means to reduce the dose of ultrasonic energy applied -to a limb in an ultrasonic tank.

Additionally, an objective of this invention is to provide an ultrasonic tank which will rotate thereby reducing the total energy of the cavitating forces on the limb surface therein exposed.

A further objective of this invention is to provide an ultrasonic tank which is pulsed thereby reducing the total energy absorbed by the limb; the threshold of biological damage Itherefore is not reached.

The above and still further objects and advantages of the present invention will become apparent upon considyeration of the following detailed description of a specific embodiment thereof, especially when taken in conjunction with the accompanying drawing herein: the character of the invention is illustrated by FIG. 1 which is a cross-section of the utlrasonic tank capable of rotation.

FIG. 2 is a cross-section of the ultrasonic tank which is pulsed.

Referring in detail to the drawing, FIG. 1 illustrates an ultrasonic tank assembly which is comprised of a tank liner 4 made of a material which will transmit ultrasound and not be easily damaged by Various cleaning chemicals and stainless steel is an acceptable material; a tank cabinet 5 having an opening at one end, power cables 2 and 3, and a power supply 1; said power supply 1 provides energy in the range of 20-400 kc. to power cable 3 which is attached at the other terminal end to the commutator set 25; attached to the bottom and sides of tank liner 4 are piezoelectric transducers 6 which are energized by connection to the commutator set 2S by power cables 7; the transducers 6 may be on the sides and on the bottom of tank liner 4 or only on the side or only on the bottom; power supply 1 also provides energy for a motor 8 by means of cables 2; motor 8.has a drive wheel 9` which serves to rim drive the rotation idler wheel 10- which in turn transmits rotational force to the wheel portion 12c of the tank support member 12; the bottom support flange portion 12d rests on ball bearing turntable 11 which is fitted onto the bottom of cabinet 5, while the upper flange portion 12a is attached to the base of the tank liner 4; the rotation idler wheel 10 is held in position by a iiXed support arm 10a within which it may rotate freely; the tank liner 4 is fitted onto a raceway of ball bearings 4a which allow the tank to rotate freely and with minimum transmission of ultrasonic vibratory energy to the tank cabinet 5 by use of ball bearings made from acoustic insulating materials; the tank assembly is supported by feet 13 which allow space for passage of the power cables to the entry in the bottom of cabinet 5 by raising the tank unit olf the resting place and by using vibration dampening materials serves the function of lessening audible noise. A germicidal solution 17 is shown having a body limb 24 in position for sterilization.

In FIG. 2 illustrates an alternative means of accomplishing the objectives of further dose reduction when operating at minimal power levels necessary for cavitation. The tank liner 14 is fitted tightly into tank cabinet 15 by means of an O-ring 14a or a non-hardening sealant material; piezoelectric transducers 16 are attached on opposing sides of the tank liner, there being at least two opposing rows and transducers may also be attached to the bottom of the tank liner; the transducers are connected by means of power cables 17 to the co-axial switches 18 which operate so that alternation of active transducer rows produces a cavitaton source which either alternates from one side of the tank to the other, or travels around the tank as suceeding rows of transducers are pulsed. A motor 19 supported by motor block 19a rotates the co-axial switch bank, power cable 20 provides energy for the motor which ordinarily wil be 110 V. AC from the power supply 21; the co-axial switches 18 are supplied with ultrasonic energy by means of power cable 22 and power supply 21. Feet 23 support the tank assembly. I have shown the coaxial switches located in the tank but they could equally well be Situated in the power supply; and, also the switching could be performed by means other than mechanical as shown here; alternatively I could have a solid state channel selector pulse the transducer rows either successively or alternately, a germicidal solution 17 is shown having a body limb 24 immersed in position for sterilization.

By these means, it is possible to further reduce the dose of ultrasonic energy to a limb, when the equipment is being operated at power levels at the lower threshold of the cavitaton phenomenon, generally about 0.03 to 5.4 watts/cm.2 depending on the solution. We have selected a frequency in the range of 70 to 90 kilocycles per second as preferential. These techniques are not new to physical medicine. In the instance of X-ray radiation therapy, where a high dose is desired at a tumor site deep in the body, the high dose to the superficial body tissues is avoided by rotating the radiation source around the sublject when prone or rotating the subject while stirring.

In ultrasonic sterilization the germicidal solutions are of prime importance. Several formulations have been recom-mended by Prange (U.S. Patent 2,970,073); a sterilizing solution called Sonitizer 17 is available from Ultrasonic Industries, Inc.; and Shaner has recommended Zephiran 1:750 to which 1% Formalin may be added; a further Shaner formula for use in ultrasonic hand scrubbing is comprised of trichlorethylene having ethyl alcohol -30-50% vol/vol., Zephiran to give 1:5 00 final concentration or iodoform to yield 400 parts per million active iodine, 0.5% vol/vol. mineral oil to replace skin oils. This latter formula has the advantage of being highly disinfectant and is fast drying in air and is reported to minimize cavitaton sensation in the hands. No soaps or detergents should be used with Zephiran due to rapid inactivation of the Zephiran.

The use of ultrasonics plus a device to attenuate the cavitaton produced by the power supply (in the range of 30-400 kc.) so that the energy is adequate to produce cavitaton yet not produce cavitaton pain in the hand or other harmful biological side effects plus a suitable sterilizing solution yields a new system of surgical hand scrubbing that should be quicker and more ecient with less danger of accidental malpractise due to cross-infection.

These and other modifications will be apparent to those skilled in the art of this invention which includes all modifications falling within the scope of the following claims.

I claim:

1. In a process for rendering the arm and hand sur gically clean, comprising immersing said arm and hand in a germicidal solution contained in a tank, positioning a plurality of sources of ultrasonic energy circumferentially spaced about said tank, said sources being directed inwardly of the tank, and sequentially pulsing at an ultrasonic frequency each said source in turn about the tank so as to create a rotating acoustic eld about the arm and hand.

2. A process for rendering the arm and hand surgically clean which comprises immersing said arm and hand in an ultrasonic tank containing a cavitating solution of germicidal chemicals activated in a frequency selected from the range of 30 to 400 kilocycles per second at an energy of `0.03 to 5.4 Watts per cm.2 wherein a plurality of sources of ultrasonic energy are circumferentially spaced about said tank, said sources being directed inwardly of said tank, and are sequentially pulsed about said tank at an ultrasonic frequency within said range so as to create a rotating acoustic lield about the arm and hand.

3. A process for rendering the arm and hand surgically clean as claimed in claim 2, wherein the circumferentially spaced ultrasonic sources are pulse successively.

4. A process for rendering the arm and hand surgically clean as claimed in claim 3, wherein the frequency is selected from the range of 70 to 90 kilocycles per second at an energy of 0.03 to 5 .4 watts per cm.2.

5. A process for rendering the arm and hand surgically clean as claimed in claim 2, wherein the circumferentially spaced ultrasonic sources are pulsed alternately.

6. A process for rendering the arm and hand surgically clean as claimed in claim 5, wherein the frequency is selected from the range of 70 to 90 kilocycles per second at an energy of 0.03 to 5.4 watts per cm?.

7. A process for rendering the hand and arm surgically clean which comprises immersing said hand and arm in an ultrasonic tank containing a cavitating solution of germicidal chemicals activated in a frequency selected from the range of 30 to 400 kilocycles per second at an energy of 0.03 to 5.4 watts per cm2 wherein the source of ultrasonic energy is attached to the tank and is moved rotationally about the immersed arm and hand by rotation of the tank.

8. A process for rendering the arm and hand surgically clean which comprises immersing said arm and hand in an ultrasonic tank containing a cavitating solution of germicidal chemicals activated in a frequency selected from the range of 70 to 90 kilocycles per second at an energy of 0.03 to 5.4 watts per cm2 wherein the source of ultrasonic energy is attached to the tank and is moved rotationally about the immersed arm and hand by rotation of the tank thereby reducing the radiation time of exposure and dose of ultrasonic energy to the arm and hand exposed to focused ultrasound.

9. An ultrasonic tank assembly comprised of a tank liner, a tank cabinet, ball bearing means; said ball bearing means being adapted to t onto the upper rim of said tank cabinet, said tank liner being tted into said tank cabinet andresting its upper portion on the ball bearing means; a ball Abearing turn table, a tank support member having an upper flange-like expansion, a rim drive wheel portion, and a support ring portion on its lower part; said tank support member having its lower part fitted inside said ball bearing turn table so that said support ring is in contact with said ball bearing turn table; said upper flange-like expansion of the tank support member being permanently attached onto the base of said tank liner; a motor, a motor bracket, a drive wheel a rotation idler wheel and support arm; said motor bracket being permanently xed to the lower part of said tank cabinet with said motor attached so that said drive wheel is vertically oriented and in contact with said rotational idler wheel, said rotational idler wheel being supported in said support arm which is permanently attached to said tank cabinet; said rotational idler wheel being in contact with said rim drive wheel portion of said tank support member; an ultrasonic power supply, piezoelectric transducers, power cables, coaxial cables, a commutator set attached to and insulated from said tank support member; said transducers being permanently attached to said tank linerthere being at least one transducer on its base and at least two transducers opposite each other on the side wall of said tank liner; coaxial cables connecting each transducer to said commutator set, coaxial cables `connecting said commutator set to said ultrasonic power supply; power cables connecting said motor to said ultrasonic power supply; and feet, said ultrasonic tank assembly being supported by said feet.

10. An ultrasonic tank assembly being comprised of a tank liner, a tank cabinet, an O-ring, piezoelectric transducers, motor, motor support, coaxial stepping switches, coaxial cable, power cable and a power supply; said tank liner being tted into said tank cabinet having said O-ring positioned at its upper rim and meeting in intimate contact with the upper part of said tank liner; said tank liner having at least one transducer exteriorly attached to its base and at least two rows of transducers exteriorly attached to the side wall of said tank liner, said rows being circumferentially spaced about said tank With each said row extending from a point adjacent to said base to a point adjacent to said upper rim; said motor support attached to the base of said tank cabinet, said motor attached to said motor support; a bank of said coaxial stepping switches having circuits equal in number to the transducers being attached to said motor; said coaxial cables connecting each row of said transducers to said coaxial stepping switches; said coaxial cables connecting said coaxial stepping switches to said power supply; said power cables connecting said motor to said power supply; feet, said ultarsonic tank assembly being supported 0n said feet, and means for mechanical stepping of energy source to rotate ultrasound around tank liner.

11. An ultrasonic tank assembly being comprised of a tank liner, a tank cabinet, and O-ring, piezoelectric transducers, solid state selector switches, power supply, coaxial cables, and power cables; said tank liner being tted into said tank cabinet having said O-ring positioned at its upper rim and meeting in intimate contact with the upper part of said tank liner; said tank liner having at least one transducer exteriorly attached to its base and at least two rows of transducers exteriorly attached to the side wall of said tank liner, said rows being circumferentially spaced about said tank with each said row extending from a point adjacent to said base to a point adjacent t0 said upper rim; said coaxial cables connecting each transducer row to said solid state selector switch housed in said power supply so as to pulse each transducer row successively or alternately, and means for electronic switching of the energy source to rotate ultrasound around the tank liner.

References Cited UNITED STATES PATENTS 1,318,740 10/1919 Fessenden 21-54 XR 2,702,260 2/1955 Massa 134-1 2,891,176 6/1959 Branson 134-1 XR 2,970,073 1/1961 Prange 134-1 2,985,003 5/1961 Gelfand et al. 134-1 XR 3,113,761 12/1963 Platzman 134-1 XR MORRIS O. WOLK, Primary Examiner JOSEPH T. ZATARGA, Assistant Examiner U.S. Cl. X.R. 21-102; 134-1, 1:84 

